Characterisation of the mechanical behaviour and the forming limits of metal foils using a pneumatic bulge test

The characterisation of metals gains increasing importance due to advanced methods in numerical simulation and design of forming processes. With conventional methods being restricted in the case of characterisation of thin metal sheets, the bulge test is a promising approach with significant advantages compared e.g. to tensile testing. While the hydraulic bulge test is on the verge of being a standard characterisation method of metal sheets in conventional length scale, little knowledge exists about the bulge test using gas pressure. For thin metal foils, requiring relatively small pressure regimes, the pneumatic bulge test offers the possibility of a significant reduction in both experimental complexity and procedure. In this paper, the pneumatic bulge test is applied for the determination of true stress true strain curves and the forming limit diagram of pure aluminium and copper sheet with thicknesses ranging from 25 µm to 100 µm. With these investigations the principle applicability of the pneumatic bulge test for the mechanical characterisation of thin metal foils is verified.